1. Field of the Invention
The invention relates to light emitting diode based lighting systems and in particular to systems in which a phosphor (photo luminescent) material is utilized to generate a desired color of light.
2. Description of the Related Art
The introduction of the solid-state semiconductor devices such as semiconductor light emitting diodes (LEDs) has allowed a new generation of lighting systems to come into existence. Today, lighting fixture designs utilizing LEDs are limited to systems in which an LED (or an array of LEDs), replaces conventional light sources such as incandescent bulbs and fluorescent lamps. As is known with conventional lighting sources a lamp or light shade is used to prevent direct viewing of the light source and for aesthetic considerations. Often the shade is made from a translucent material, such as card, woven material or a plastics material, or from glass. Moreover, the shade can be made of a colored material and acts as a filter to impart a desired color to light transmitted by the shade.
In order to produce a selected color of emitted light, LEDs often incorporate a phosphor layer whose light, emitted in response to an excitation radiation (light) from the LED, combines with light from the LED to produce the selected color of emitted light. It is common in such lighting systems to incorporate further elements such as a light reflection planes, light diffusing components, and color filters.
Typically the phosphor is incorporated in the LED chip package during fabrication of the LED and in close proximity to, or in contact with a light emitting surface of the LED chip. Often, the phosphor layer is coated directly onto the LED to achieve a desired intensity and color of generated light. As disclosed in our co-pending U.S. patent application Ser. No. 11/640,533, the content of which is hereby incorporated by way of reference thereto, the phosphor can also be provided on a surface of an optical component or integrally incorporated into the component, typically a lens, for ease of fabrication of the LED package. The present invention arose in an endeavor to provide an improved lighting system which is based entirely on solid-state components, but which is enhanced by providing greater flexibility in generated light output.